Hi, The sequence with the topless (male) dancers was from a short film shown on the BBC. I didn't realise it was on Omnibus but I saw it when it went out in the summer of '78.
The film was about "dance culture" in the north of England and was a pretty flimsy affair. It focused on three genres: Heavy rock/metal, "Roxy" and Northern Soul. The whole thing couldn't have been more than ten minutes long.
Each segment was short, just the length of the song they were dancing to. There was no dialogue that I recall. It just went from one segment to the next.
The heavy rock section featured a dance hall full of greasers dancing in an elaborate "spread" manner. The "Roxy" section (Bowie/Roxy Music, etc) featured a club in Manchester I think. The Northern guys were dancing to Afternoon of The Rhino. Whether they were actually dancing to this or it was overlaid I don't know but this was definitely the music and they did appear to be in synch.
As I recall (I was in the 6th form at the time) there was a brief review in the paper the next day, Guardian or Times probably, where the director/maker was accused of going "astray" on some parts. I think this was on the Roxy segment which may have appeared too avant garde or unrepresentative for the reviewer. I remember that the Northern Soul segment received more favourable comments.
I'm pretty sure that the intro music to the film ( as a whole, not just the Northern section) was Interplay. I'm not sure about this but I think that the clip of film which features in some youtube films of the girl dancing in the Casino (spinning /long skirt/white socks/polyveldts) may have been in the Interplay intro. She looks like the same girl dancing to Rhino